It is common for maintenance vehicles to travel along a railroad track while performing various types of rail maintenance operations. The use of such machines must be planned around the schedules of trains using the rails. When a side rail or loading rail is not readily available, provision must be made for removing the transporter from the track to permit the regular scheduled train to pass.
In addition to regular rail maintenance, there is also a need for heavy duty vehicles such as hydraulic crawler cranes to be used at a rail site. For example, in the case of a train wreck or derailment, a crane may be necessary to move heavy rail cars and assist in clearing the tracks. Frequently, it is necessary to perform such work at locations where roadway access is limited or even nonexistent. Any attempt to rely on roadway travel in such situations could delay the arrival of necessary equipment. In such emergency situations, time is generally of the essence.
Vehicles and machines presently used for this type of operation can in general be removed from the main track only at specially prepared landings, or at existing track sidings. Since special landings and sidings are often quite far apart, considerable working time is lost while proceeding to, waiting at, and returning from the place at which the maintenance machine can be removed from the track. Further, since trains frequently fail to rigidly adhere to schedules, removal of the vehicles in anticipation of the arrival of the train can often lead to considerable delays and lost time.
Transport of heavy duty crawler cranes on rail carriers creates unique problems. For example, a standard carrier is normally about 8 feet wide. This width limitation is occasioned by conventional rail spacing which in turn frequently determines available side clearance along the rail bed. The longitudinal carrier deck dimension can readily accommodate the tracks of a heavy duty crawler crane which generally extends about 18 feet, but the limited 8 foot width does not allow for maneuvering a crane along the length of the carrier. Thus to load and carry such a crane onto a carrier, either a special load site or platform is required which would permit direct end loading, that is driving of the crane directly onto the platform from either end, or the crane must be loaded and carried perpendicular (broadside) to the longitudinal access. The former solution is expensive and not practical because of the location of the carrier wheels at opposite ends of the carrier. The latter solution is not practical because the crane would extend considerably beyond each side of the carrier and would not clear many obstructions along the track.